Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/02—Transmitters
  • H04B1/04—Circuits
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/34—DC amplifiers in which all stages are DC-coupled
  • H03F3/343—DC amplifiers in which all stages are DC-coupled with semiconductor devices only
  • H03F3/3432—DC amplifiers in which all stages are DC-coupled with semiconductor devices only with bipolar transistors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R21/00—Arrangements for measuring electric power or power factor
  • G01R21/10—Arrangements for measuring electric power or power factor by using square-law characteristics of circuit elements, e.g. diodes, to measure power absorbed by loads of known impedance
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/189—High-frequency amplifiers, e.g. radio frequency amplifiers
  • H03F3/19—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/34—DC amplifiers in which all stages are DC-coupled
  • H03F3/343—DC amplifiers in which all stages are DC-coupled with semiconductor devices only
  • H03F3/3432—DC amplifiers in which all stages are DC-coupled with semiconductor devices only with bipolar transistors
  • H03F3/3435—DC amplifiers in which all stages are DC-coupled with semiconductor devices only with bipolar transistors using Darlington amplifiers
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/456—A scaled replica of a transistor being present in an amplifier
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/465—Power sensing
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/75—Indexing scheme relating to amplifiers the amplifier stage being a common source configuration MOSFET

Definitions

• the invention is in the field of transistor amplifier circuits, and relates more particularly to power amplifier circuits and power detection circuits for such power amplifier circuits.
• Amplifiers of this general type are frequently used m high-frequency RF amplifiers, such as those used in wireless communications apparatus, as well as in audio amplifiers and other applications In such amplifiers, particularly when used in RF applications, it is desirable to provide an indication of the power in the output stage
• this function is typically accomplished by one of two techniques
• a directional coupler or voltage divider may be provided at the output of the power amplifier to sense a fraction of the signal applied to the load, and this sample signal is then used to indicate the power in the load
• the second technique used in the p ⁇ or art generates a sample of the current in the power amplifier by using a smaller transistor in parallel with the power transistor The sample current is then fed off-chip, where it is averaged and used to provide an approximate indication of the power in the load
• a new power detection circuit for use in a power amplifier circuit having an amplifying transistor, in which the power detection circuit includes a circuit for generating a signal which is directl) proportional to a power level in the amplifying transistor
• this is done by providing a circuit for generating a voltage proportional to the square of a current in the amplifying transistor and averaging this voltage to provide an indication of this power level in the amplifying transistor
• a wireless communications device having an RF power amplifier circuit is provided with a power detection circuit for generating a signal which is directly proportional to the power level in the amplifying transistor
• the power detection circuit may be implemented using a simple MOS transistor configuration, or a trans near circuit using bipolar transistors which is more complex than the MOS circuit but which provides greater accuracy
• a power detection circuit in accordance with the present invention offers a significant improvement in that a particularly advantageous combination of features, including a compact and efficient design, and more accurate performance, can be obtained in an economical and easily-implemented configuration
• Fig 1 shows a simplified partially-block and partially-schematic diagram of a power amplifier circuit having a power detection circuit in accordance with the invention
• Fig 2 shows a simplified schematic diagram of a power detection circuit in accordance with a first embodiment of the invention
• Fig 3 shows a schematic diagram of a power detection circuit in accordance with a second embodiment of the invention
• a power amplifier circuit 10 for amplifying an input signal NiN at an input terminal 12 is shown in simplified partially-block and partially-schematic form m Fig 1
• the power amplifier circuit includes an amplifying transistor 14 for amplifying the input signal NiN provided to the base of the transistor 14 from the input terminal 12 through an input matching network 16
• the power amplifier circuit may be used in va ⁇ ous applications, such as audio amplification, or RF amplification in such areas as wireless communication and internet connection, so that the input signal VIN may be either an audio or RF input signal
• the power amplifying transistor 14 is biased from the power supply voltage Vcc by a bias network 18
• circuit portions such as input matching network 16 and bias network 18 which are shown in block-diagram form can be implemented by va ⁇ ous known circuit configurations familiar to those of ordinary skill in this art, and are accordingly not desc ⁇ bed in further detail herein
• the output circuit of power amplifier 10 is shown in simplified form as including a collector resistor 20 and an output matching network 22 for providing an output voltage Nou ⁇ at output terminal 24 to supply power to a load symbolically illustrated by resistor 26
• a proportional sample of the current in the power amplifier transistor 14 is obtained by using a smaller transistor 28 having its base- emitter circuit connected in parallel with that of the power amplifying transistor 14
• the present invention uses a squa ⁇ ng and averaging circuit 30, having its input coupled to the output of transistor 28, in order to generate a voltage which is proportional to the square of the current in sensing transistor 28, and then averaging this voltage Circuit 30 generates an output signal VDET at terminal 32 which is directly proportional to the power level in the amplifying transistor 14 and which is a substantially more accurate representation of this power level than can be obtained using the p ⁇ or-art technique, since the power level is proportional to the mean square of the current level in the amplifying transistor
• This technique permits the implementation of a power detection circuit which can be integrated on the same die as the power amplifier circuit and which can generate a voltage which is an accurate representation of the power in the amp
• sense transistor 28 has a base connection (as shown by the vertical dashed line) to the base of transistor 14, as shown more fully in Fig 1, and has its collector coupled to Vcc by a se ⁇ es connection of a resistor 34 and a diode-connected PMOS 36
• the collector of sense transistor 28 is also coupled to the gate of a second PMOS transistor 38, with transistor 36 serving to generate a threshold voltage for transistor 38 and the current through resistor 34 generating a voltage applied to the gate of transistor 38 to generate a squared current in transistor 38
• This squared current is passed through resistor 40 to generate a detector output voltage VDET at terminal 32 which is directly proportional to the power level in the amphfying transistor
• a capacitor 42 is provided in parallel with resistor 40 to form a simple RC averaging circuit, so that the detector output voltage VDET IS an averaged signal which accurately represents
• FIG. 3 A second embodiment of the power detection circuit, using a bipolar implementation with a transhnear circuit, is shown in Fig 3 This embodiment is less compact and more complex than the embodiment of Fig 2, but offers the additional advantage of still greater accuracy
• sense transistor 28 has its base connected as in Figs 1 and 2, and has its collector coupled to a current mirror composed of bipolar transistors 44 and 46 connected in a conventional current-mirror configuration
• the collector of transistor 46 is connected both to a se ⁇ es connection of diodes 48 and 50 and to the base of transistor 52
• the emitter of transistor 52 is connected to the base of transistor 54 and to the collector of transistor 56, which, in combination with transistor 58 and current source 60, forms a second current mirror
• diodes 48 and 50 and transistors 52 and 54 form a transhnear circuit configuration in which the sum of the voltages across the two diodes is equal to the sum of the voltages across the two base-emitter junctions of transistors 52 and 54, and in which the product of the currents m the two transistors is equal to the product of the current in the two diodes
• the current in transistor 54 being proportional to the square of the current in sense transistor 28 divided by the current in transistor 52 Since the current in transistor 52 is
• the present invention provides a power detection circuit for a power amplifier circuit suitable for use in RF or audio amplifiers, in which an output is generated which is directly proportional to the power level in the amplifying transistor Circuits in accordance with the invention are compact, efficient, easily implemented and provide a signal which more accurately represents the power level in the amplifying transistor than do p ⁇ or-art circuits

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2000
  • 2000-04-13 US US09/548,726 patent/US6448855B1/en not_active Expired - Lifetime
• 2001
  • 2001-04-03 DE DE60128560T patent/DE60128560T2/de not_active Expired - Lifetime
  • 2001-04-03 CN CNB018009123A patent/CN1214520C/zh not_active Expired - Fee Related
  • 2001-04-03 EP EP01927856A patent/EP1277274B1/de not_active Expired - Lifetime
  • 2001-04-03 JP JP2001577700A patent/JP5134176B2/ja not_active Expired - Fee Related
  • 2001-04-03 WO PCT/EP2001/003755 patent/WO2001080421A2/en not_active Ceased
  • 2001-04-03 AT AT01927856T patent/ATE363152T1/de not_active IP Right Cessation
  • 2001-04-03 KR KR1020017015988A patent/KR100805398B1/ko not_active Expired - Fee Related

Non-Patent Citations (1)

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